Recently, Liu Shengzhong, a researcher of the Thin Film Silicon Solar Cell Research Group (DNL1606), Dalian Institute of Chemical Physics, Chinese Academy of Sciences, and Yang Dong, a researcher from Shaanxi Normal University, formed a photoelectric conversion by combining a translucent perovskite battery with a high-efficiency silicon heterojunction thin-film battery. A four-terminal perovskite-silicon stacked solar cell with an efficiency of 27.0%.
Crystalline silicon solar cells are the first generation of solar cells. After decades of development, the technology has become very mature. Currently, 95% of the photovoltaic market share is occupied by crystalline silicon solar cells. The photoelectric conversion efficiency of the best crystalline silicon solar cells reported by the laboratory has reached 26.6%, very close to its theoretical photoelectric conversion efficiency limit of 29.4%. Under the laws of physics, the road to improving the efficiency of crystalline silicon cells is becoming increasingly narrow. In order to achieve higher photoelectric conversion efficiency, more and more researches have begun to focus on crystalline silicon batteries and other high-efficiency batteries to form stacked batteries.
Perovskite battery is the third generation solar cell developed in recent years. It has the advantages of abundant raw materials, low cost, simple preparation process and good tolerance to defects. At present, the photoelectric conversion efficiency of perovskite batteries reported by the laboratory has exceeded 24%. The structural formula of perovskite is ABX3, the A position is usually a positive monovalent organic cation CH3NH3 +, NH = CHNH3 + or inorganic Cs + ion, etc., and the B position is usually a positive divalent metal cation Pb2 +, Sn2 +, etc. X is usually a halogen anion I-, Br-, Cl-, etc. Through ion replacement, the band gap of perovskite can be flexibly adjusted from 1.4 to 2.3 eV, making it a very ideal material for laminated battery sub-batteries.
The laminated battery is composed of a high band gap sub-cell and a low band gap sub-cell. The low-bandgap sub-cell broadens the utilization rate of sunlight photons; the high-bandgap sub-cell reduces the heat energy loss during the relaxation process of the electron transition after the semiconductor captures the high-energy photon. Therefore, the stacked battery has higher ultimate photoelectric conversion efficiency than the single junction battery. One of the keys to obtaining a high-efficiency stacked solar cell is to prepare a transparent electrode under mild conditions, that is, to produce an electrode with both high conductivity and high light transmission without harming the underlying material.
The team used vacuum thermal evaporation to deposit thin films, using the molybdenum trioxide / gold nanonet / molybdenum trioxide "sandwich structure" as a transparent electrode to replace the metal back electrode in traditional perovskite batteries. The prepared translucent perovskite solar cell has a photoelectric conversion efficiency of 18.3%, which is currently one of the highest efficiencies of translucent perovskite cells prepared using ultra-thin metals. Combining this translucent perovskite solar cell with a silicon heterojunction thin film cell with a photoelectric conversion efficiency of 23.3%, a four-terminal stacked solar cell with a photoelectric conversion efficiency of 27.0% was obtained.
This study used a simple and low-cost method to prepare transparent electrodes with high conductivity and high light transmittance, which helped promote the development of translucent batteries and multi-junction / stacked batteries, reducing the cost of photovoltaic power generation. Related results were published in "Advanced Functional Materials" (Advanced Functional Materials). This work was supported by the National Natural Science Foundation of China, the National Key Research and Development Program of China, and the Shaanxi Science and Technology Innovation Guidance Project.
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